Generation of a recombinant Fab antibody reactive with the Alzheimer's disease-related Aβ peptide

A recombinant Fab antibody, designated 1E8-4b, which reacts with the Alzheimer's disease (AD)-related Abeta peptides, Abeta[1-40], Abeta[1-42] and Abeta[1-43] has been developed. The 1E8-4b Fab was constructed by cloning the VHCH1 and VLCL domains from the parent hybridoma 1E8 antibody, reported previously to recognize these Abeta peptides. Briefly, a C-terminal Flag tag sequence was incorporated into this construct, which was ligated into the vector pHFA(2) and expressed in Escherichia coli. Following purification on an M2 anti-Flag affinity column, the 1E8-4b recombinant Fab antibody was shown to bind plaques within sections of brain tissue from CERAD-defined AD patients by immunohistochemistry. ELISA, epitope mapping and immunoblotting confirmed the recognition of the Abeta[1-40/42/43] peptides by the 1E8-4b Fab. The 1E8-4b Fab did not recognize APP695 or APP770 which contain the Abeta sequence. The Abeta specificity of the recombinant 1E8-4b Fab antibody was identical to the parent 1E8 monoclonal antibody.